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jet size

  • Thread starter Thread starter Gs1100e82
  • Start date Start date
Tom R said:
Keep in mind most here are familiar with the Dynojet kits. The factory pro needles have a much different taper that almost looks stock. When I bought my needles from ray, I think he said I'd end up somewhere around 140 - I tried 138.5, 140, 142.5 and 145's before I settled on 142.5's. But as was stated earlier, every bike's a bit different - you'll just have to experiment. Luckily, the pods simplify removing the carbs because you're going to have to do it several times. Btw 47.5 is common pilot jet and you can change clip position with the carbs on the bike.
Click to expand...

Are you saying with a stock GS1100 16V pods and pipe but using a Factory Pro needle you needed at MK142.5 Main instead of a MK127.5???

Did you do plugs chops or use a WB02 and how did you determine the main jet setting?
 
I wish I had a wide band, but just plug chops - yes Mikuni jets. When I bought the bike it had the current pods, a rusty V&H megaphone, stock needles raised up and 142.5 jets - I put in some '83 cams and the super sport exhaust. Supposedly it was dyno tuned by a shop in Markham by previous owner, but who knows. It's always pulled great on the top end, but feels much better in the midrange now.
 
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Tom R said:
I wish I had a wide band, but just plug chops - yes Mikuni jets. When I bought the bike it had the current pods, a rusty V&H megaphone, stock needles raised up and 142.5 jets - I put in some '83 cams and the super sport exhaust. Supposedly it was dyno tuned by a shop in Markham, but who knows. It's always pulled great on the top end, but feels much better in the midrange now.
Click to expand...

I would think that either the pods are worn thin and not filtering anything (have you ever oiled them? are they K&N?) or those FP needles are so much thicker than a DJ needle that you have to over size the main to compensate.

A MK142.5 is about DJ152 and that is much larger than a DJ138 (biggest in stage 3 3133 kit). A MK142 is what you should need with 4:1 Pods and 1166 BB kit!!!
 
Like I said earlier, K&N knockoffs - or maybe they are K&N's - the only difference I can see is they don't say k&n on the chrome cap. Btw, I know how to clean and oil pods. What do you want me to say? The bike pulls hard to redline.
 
Tom R said:
Like I said earlier, K&N knockoffs - or maybe they are K&N's - the only difference I can see is they don't say k&n on the chrome cap. Btw, I know how to clean and oil pods. What do you want me to say? The bike pulls hard to redline.
Click to expand...

You don't have to get defensive, assuming you are reasonably well jetted it suggests the DJ and FP needles are completely different even to the point of changing the main.
 
You have a Factory Pro kit so follow the directions. I'd start with the 130 main jet and set the needle per instructions.
If you have a 50 pilot jet lose it for a 47.5.
 
chef1366 said:
You have a Factory Pro kit so follow the directions. I'd start with the 130 main jet and set the needle per instructions.
If you have a 50 pilot jet lose it for a 47.5.
Click to expand...

I hear that my stock 1100 should run mk155's when using a FU kit
 
thanks tom. i appriciate your input. im still waiting to recieve the next two sizes up on the main jets. when they get here ill post how it went.
should be here today
 
Gs1100e82 said:
hey guys, own a 1982 gs1100ez and it has a vance and hines race 4 into 1 pipe, and i just bought k&n individual pods for it. i also just purchased a factory pro
3.0 kit for the carbs to be rejected. the kit came with 130 and 132.5 main jets
i put in the 132.5 jets and the bike is still getting flat between 7-9k. i set the float heights to 22.4mm. the low and midrange is in my eyes perfect. smooth and powerful. i had already also synchronized the carbs. i pulled a spark plug and it looks lean for sure. i called factory pro and they said i may need a bigger main jet size. so he is going to send me the next two sizes up for free. at least they seem to be taking care of me on that but from what i have read on here it seems everyone has been good with running around 125s in their bike. any ideas?
Click to expand...




I just spoke to Rapid Ray about the FP needles v.s. DJ needles. He confirmed they were very different with the Dj main jet being the the MK122.5-MK127.5 (DJ132-DJ138)range and the FP main jet being MK130-MK132.5 range.

While I understand that there is overlap between needle and main jet, it is hard to imagine that there is that much overlap at WOT beyond red line which is where the main jet sizing is adjusted to. Without a WB02 you will never see that, and so it would be easy to based jetting on power pull in the 7000-9000 RPM area where you are still somewhat on the needle (apparently so).

Ray said that he thought the FP needles were easier to tune, that the needles were closer to stock taper than the DJ needles and that he usually went back to the stock #45 pilot using the FP needle whereas the DJ normally requires the bump to 47.5

Other than that he did not provide any more specifics. I'm still trying to get my head around, it and eve considering the FP needles for a rejet of my bike. The problem is I need a find a big big hill around here somewhere.

My jetting is a little off in the mid range since I moved from SB to Tucson.
 
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just got the new jets in. 135, 137.5. i put the 137.5 in first and ill run it probably monday when i can get a chance. hopefully this is going to remedy the issue. or even if i get it too rich id just back it to the 135's. ill repost on progress
 
posplayr said:
You don't have to get defensive, assuming you are reasonably well jetted it suggests the DJ and FP needles are completely different even to the point of changing the main.
Click to expand...

No worries, I was just throwing you a bit of what you gave to the OP - probably came off wrong. Interestingly enough, the needles from a rack of bs32 carbs I have are fairly close in size and taper to the FP - more so than the 1100 bs34 carbs. It's been a couple of years, but I did a check with a set of calipers and a fine tip sharpie and wrote down the results on the back of an envelope. Very scientific.
If I enjoyed taking carbs on and off more, I would have tried to run them. Anyone know if this has been tried?
 
Tom R said:
No worries, I was just throwing you a bit of what you gave to the OP - probably came off wrong. Interestingly enough, the needles from a rack of bs32 carbs I have are fairly close in size and taper to the FP - more so than the 1100 bs34 carbs. It's been a couple of years, but I did a check with a set of calipers and a fine tip sharpie and wrote down the results on the back of an envelope. Very scientific.
If I enjoyed taking carbs on and off more, I would have tried to run them. Anyone know if this has been tried?
Click to expand...

I think it is scientific. All the main jet gas has to flow through the needle to emulsion tube gap so for the same bike the main jet size will be proportionately related to the tip thickness at full slide height. For example if the tip is. Thicker reducing the flow past the needle the main needs to be larger to get the same afr.

I'm not assuming it is linear or can even be done by equivalent areas but it should be monotonically consistent to a first order.
 
posplayr said:
I think it is scientific. All the main jet gas has to flow through the needle to emulsion tube gap so for the same bike the main jet size will be proportionately related to the tip thickness at full slide height. For example if the tip is. Thicker reducing the flow past the needle the main needs to be larger to get the same afr.

I'm not assuming it is linear or can even be done by equivalent areas but it should be monotonically consistent to a first order.
Click to expand...

I was kidding about my methods being very scientific - but, now I'd like to find that envelope again so I could post what I found. If I remember right, the tips were all the same diameters - or within a couple thousandths.
At the time, it struck me that the 850 needles would make the bike run richer.
 
Tom R said:
I was kidding about my methods being very scientific - but, now I'd like to find that envelope again so I could post what I found. If I remember right, the tips were all the same diameters - or within a couple thousandths.
At the time, it struck me that the 850 needles would make the bike run richer.
Click to expand...

Not perfectly scientific :o
 
OK so last night i installed the 137.5's in the carbs and put the carbs back on the bike. syncronized the carbs again using my motionpro tool. i havent been able to get it out for a ride which will of course be the true test. BUT, i can tell you that the bike runs very well and as far as reving up, before with the 132.5's i had to sort of hold on the throttle for a second or 2 to get it to rev to 7000rpm. now will very little effort and a few blips it goes right up to 8-9k. i can only assume till i ride it is that im on the right track. possibly hit a home run this time
 
so yesterday i got to finally ride her after installing the 137.5s. it ran much much better. between 7 and 9k the bike was finally pulling a bit, but i am not convinced it is enough yet. i called factory pro and they are sending me the next two sizes up. i think one or two more up will do the trick.
 
GS1100e82, just for giggles try using the 47.5 pilot jets, setting your jet needle in the center position and running the 137.5 Mikuni main jets. ;)
 
what exactly does the pilot jet do? i assumed that the one they gave me would have been the right one but now your the second or third person to say 47.5 is a good way to go.
 
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